Depending on the size, I probably wouldn't bother with AP on lasers. If you want something punchier for module sniping on an all-laser build, I'd rather go with pulses, but bursts don't have a bad AP as they are either. Unless you're fighting something extra tough (Corvette, FGS,...) with small weapons, you won't have problems with penetration.Hmmm. struggling to choose between no fall off at all or added armor piecing for the brust lasers.... I'm settled with dual'ing either pairs, instead of mixing them.
Even with the dual focused (G3), the heat seems manageable.
So use the slot for some more useful secondary effects.